Comparative analysis of Microcystis buoyancy in western Lake Erie and Saginaw Bay of Lake Huron.
Paul A Den Uyl, Seamus B Harrison, Casey M Godwin, Mark D Rowe, J Rudi Strickler, Henry A Vanderploeg
Author Information
Paul A Den Uyl: Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan, 4840 South State Road, Ann Arbor, MI 48108, United States.
Seamus B Harrison: Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan, 4840 South State Road, Ann Arbor, MI 48108, United States.
Casey M Godwin: Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan, 4840 South State Road, Ann Arbor, MI 48108, United States. Electronic address: cgodwin@umich.edu.
Mark D Rowe: National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory, 4840 South State Road, Ann Arbor MI 48108, United States.
J Rudi Strickler: Department of Biological Sciences, University of Wisconsin-Milwaukee, 600 East Greenfield Avenue, Milwaukee, WI 53204, United States; Marine Science Institute, The University of Texas at Austin, 750 Channel View Drive, Port Aransas, TX 78373, United States.
Henry A Vanderploeg: National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory, 4840 South State Road, Ann Arbor MI 48108, United States.
Microcystis is the predominant genus of harmful cyanobacterium in both Lake Erie and Saginaw Bay of Lake Huron and has the capacity to regulate the buoyancy of its colonies, sinking under certain conditions while floating towards the surface in others. Understanding the factors that control buoyancy is critical for interpretation of remote sensing data, modeling and forecasting harmful algal blooms within these two systems. To determine if Microcystis colony buoyancy in the two lakes responds similarly to diurnal light cycles, colony buoyant velocity (floating/sinking terminal velocity in a quiescent water column) and size were measured after manipulating the intensity of sunlight. Overall, there were more positively buoyant (floating) colonies in Lake Erie while most of the colonies in Saginaw Bay were negatively buoyant (sinking). In Lake Erie the colonies became less buoyant at increased light intensities and were less buoyant in the afternoon than in the morning. In both lakes, apparent colony density was more variable among small colonies (< 200 µm), whereas larger colonies showed a diminished response of density to light intensity and duration. These findings suggest that colony density becomes less plastic as colonies increase in size, leading to a weak relationship between size and velocity. These relationships may ultimately affect how the bloom is transported throughout each system and will help explain observed differences in vertical distribution and movement of Microcystis in the two lakes.
